The present invention generally relates to interlock devices, particularly to interlock devices allowing opening of enclosures only under certain circumstances, and specifically to interlock devices for electrical control boxes allowing opening of the box only when power has been switched off.
In various applications, it is desirable that enclosures can only be opened under certain circumstances. As an example, electrical control boxes should be opened only after power to the electrical controls located in the interior of the box has been interrupted to reduce the risk of electrical shock by contact with the electrical controls. Therefore, interlocks have been developed which require a master switch to be in an off position before the door to the control box can be opened. Conventionally, such interlocks were accomplished by having the shaft which operates the master switch extending through an opening in the face of the door of the control box. The shaft included an abutment which in the switch-off position was aligned with a slot allowing the door to be opened but when not in the switch-off position was not aligned with and was unable to pass through the slot preventing the door from being opened. An example of such an arrangement where abutment occurred inside of the box is shown in U.S. Pat. No. 1,443,867. However, there are circumstances where an interlock is desired but for whatever reason, the shaft which operates the master switch can not be located through the face of the door of the box. Such a circumstance exists utilizing the mechanism shown in U.S. Pat. No. 5,510,587 where the entire front face is desired to be pushed to de-energize the electric circuit.
Thus, a need has arisen for an interlock device which prevents opening an enclosure except under certain circumstances and which is operable from other than the face of the door or closure of the enclosure.